If you were to have a set of electrodes horizontal (i.e. running parallel to the floor). But are only accessible from above, i.e. the only way incident energy could inflict harm is in an upwards direction, should this in fact be considered as a vertical arrangement.

I'm guessing what the standard means by horizontal or vertical arrangement is whether the electrodes are perpendicular or parallel to the human (head to feet). I think what I am describing is the vertical arrangement rotated 90 degs, including the human.

Hopefully this make sense or am I talking rubbish.

Thanks

Makes good sense to me though I wonder how such an arrangement could occur? Is is a pullbox with terminations?

Thanks for the reply. This is in the context of an LV link box used for re-configuration of LV underground distribution feeders.

The link box would be contained in a buried enclosure and accessed from ground level via a removable covering. Please see image below.

So the thought was the worker would remove the covering and would be looking down on the conductors.

Yes. During the testing the calorimeters were placed in front of the electrodes. Horizontal electrodes were "aimed" at the calorimters and vertical ran parallel.

(usual required disclaimer - this is just my view and is not meant to be an official statement from IEEE)

The direction of the opening in relationship to the person working should match the guidelines. If the opening is perpendicular to the floor or parallel to the floor is somewhat irrelevant.

Vertical and Horizontal, can also be looked at as Parallel & Perpendicular depending on where the worker is with respect to the electrode orientation while the task is being accomplished. The model is based on specific test protocols. You need to select the one that best approximates the hazard the worker is exposed to. IN SOME CASES that my require doing AF analysis twice because what is conservative for arcing current may not be conservative for incident energy, or visa versa.

For example, to ensure you are conservative with respect to Iarc you want to make sure you are considering the "lowest possible" arcing current when setting protection thresholds. So for a VERY larger box or opening you may want to calculate an "open" (?OA)arcing current, use that value to asses if your protection is sufficiently sensitive and fast at that lower Iarc. Then calculate incident energy with a ?CB electrode model to ensure for possible higher energy. The point is that if the calculation is not "exact" it must err in the "conservative" direction.